1. Field of the Invention
The present invention relates generally to the field of machine operations on continuous web materials, and more particularly but not by way of limitation, to the control of intermittent and continuous work stations in a panel forming line which cuts accurately measured lengths of a flexible strip material and forms the lengths into profiled panels.
2. Discussion of the Prior Art
In the past, various methods have been employed for coupling an intermittently performed machine operation, such as shearing, in a continuously moving line, such as a roll forming operation on a flexible sheet or strip of metal. Basically, three types of automatic shearing machines have been used: those in which the travel of the strip material is stopped for actuation of the shearing station; those in which the strip travel is slowed and rapid action shears are used, with the shears effecting a momentary halt to the strip travel; and those using a moving shear assembly to compensate for strip travel.
Because of the high cost, both manufacturing and upkeep, of automatic shearing stations using moving or flying shears, prior art solutions have incorporated the hump table as a method for providing a variable inventory of strip material within the boundaries of the line operations. That is, a loop of the flexible strip material is caused to be formed at the intermittent work station so that the material can be continuously fed to other work stations while being stopped to accommodate the intermittent operation. This permits those operations, such as shearing and punching, to be performed on the stopped strip portion as inventory in the hump momentarily accumulates.
In Kortan, U.S. Pat. No. 3,393,547, a metal strip 2 is fed from a coil reel 1 through a prenotching press 5, forming mill 13 and punch cut-off 20. Loop pits 4 and 12 are provided on either side of press 5, and light indicators 14 maintain loop conditions. Thus, the continuous roll forming mill 13 is accommodated as is the intermittent prenotching press 5. Similarly, Kortan et al., U.S. Pat. No. 4,365,492 teaches the use of festoons, or loops, 13 and 14 in a strip line.
In O'Connor, U.S. Pat. No. 2,867,824, a strip 28 is fed from reel 32 through punch press 44 and rolling apparatus 34 to a coiling mechanism 38. The rolling apparatus 34 comprises a plurality of roller sets 36, 50 that are continuously driven to fold the strip progressively, while the punch press 44 is intermittently actuated. A loop 48 in the sheet material strip is maintained between the punch press 44 and the rolling apparatus 34. No disclosure is provided as to the forming and maintenance of the loop 48.
In Primich et al., U.S. Pat. No. 3,978,703, a hump table 30 is provided between a feeder and straightener unit 18 and a speed control station 32. A strip of material 10 is provided at a constant rate from a feed coil 12. The strip 10 is slowed via driver and pinch rollers 40, 56 of the speed control 32 as the leading edge of the strip 10 passes by micro switches 100, 104 disposed along a discharge table 38. In a specified timing sequence, shear 36 is actuated while the speed of the strip has been slowed, during which time the upstream portion of strip 10 is caused to hump over the hump table 30. This hump is dissipated once shearing has occurred and the slowed portion of strip 10 is accelerated to the higher traveling speed of the unreeling feed stock by the rollers 40, 56.
In Cauffiel, U.S. Pat. No. 3,768,349, two loops are formed. The first one over hump table 46 and the second one over hump table 56. The first hump (hump table 46) forms due to continuous feed of strip material 26 at the front end via leveler station 34, which serves to drive and straighten the uncoiling material, and due to the slow down of the strip material 26 by a pair of quick-closing, slow down rolls 50, 52 of a material-engaging and retarding unit 54. The second hump (hump table 56) is formed as material is momentarily stopped by the cutting actuation of the shear 64. The first loop, designated by the numerals 70, 76 and 80, varies in size, or material inventory, during the timing sequence of the operation.
Other patent teachings of general interest in this field include the following: Black, U.S. Pat. No. 2,165,917, teaches a hump table 52 disposed between an uncoiling and leveling unit 8 and a shearing unit 10. Smith, U.S. Pat. No. 4,158,301, also teaches a hump table 16 positioned immediately downstream of apparatus 10 which serves to withdraw coil sheet material 15 from a roll 12 to remove coil set therefrom; Gentile, U.S. Pat. No. 4,375,759, shows a hump formed between a decoiling arrangement and a press; and Plegat, U.S. Pat. No. 3,808,861, shows a stock accumulator 5 downstream of a joining device 4.
Several of these prior art teachings have recognized the advisability of stopping the traveling strip for processing by a fixed based, intermittently actuated unit operation, such as the aforementioned shearing or punch stations. Also, recognition has been given to the fact that systems which require the feed of web stock to operate at more than one speed have been difficult and costly to make. The mass of a coil stock creates an inertia consideration, and thus it has been generally regarded as best to look to constant feed rate mechanisms on the front end of such machining lines. By storing an inventory of the strip on the machine line, the continuous nature of some of the work stations could be accommodated as well as the intermittently actuated stations. In sum, compromise of line speed or lengthy run out tables has had to be incorporated in various fashions, and have almost totally sacrificed flexibility of operator and material assignment; that is, concessions given to the continuous nature of some of the work stations have often been made which establish or at least markedly restrict the way that the machine line is operated with regard to material runs, operating personnel needed, etc.